Heat, movement, sunlight may power your smartphone

Sunlight, heat in a room and even movements may soon power your portable and wearable gadgets such as smartphones, thanks to a material identified by scientists that can extract energy from multiple sources at the same time.
Researchers from the University of Oulu in Finland have found that a mineral with the perovskite crystal structure has the right properties to extract energy from many forms of energy that surround us and is normally wasted.
Perovskites are a family of minerals, many of which have shown promise for harvesting one or two types of energy at a time - but not simultaneously.

One member may be good for solar cells, while other my be good at harnessing energy from changes in temperature and pressure.
Yang Bai and his colleagues studied a specific type of perovskite called KBNNO, which may be able to harness many forms of energy.
Like all perovskites, KBNNO is a ferroelectric material, filled with tiny electric dipoles analogous to tiny compass needles in a magnet.

When ferroelectric materials like KBNNO undergo changes in temperature, their dipoles misalign, which induces an electric current.
Electric charge also accumulates according to the direction the dipoles point. Deforming the material causes certain regions to attract or repel charges, again generating a current.

Previous researchers have studied KBNNO's photovoltaic and general ferroelectric properties, but they did so at temperatures a couple hundred degrees below freezing, and they did not focus on properties related to temperature or pressure.
The new study represents the first time anyone has evaluated all of these properties at once above room temperature, said Bai.
The experiments showed that while KBNNO is reasonably good at generating electricity from heat and pressure, it is not quite as good as other perovskites.
Perhaps the most promising finding, however, is that the researchers can modify the composition of KBNNO to improve its pyroelectric and piezoelectric properties.

"It is possible that all these properties can be tuned to a maximum point," said Bai, who, with his colleagues, is already exploring such an improved material by preparing KBNNO with sodium.
Within the next year, Bai said, he hopes to build a prototype multi-energy-harvesting device. The fabrication process is straightforward, so commercialisation could come in just a few years once researchers identify the best material.
"This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable," he said.
This kind of material would likely supplement the batteries on your devices, improving energy efficiency and reducing how often you need to recharge.

The research was published in the journal Applied Physics Letters.